Neutrase hydrolysis of WPC produces hydrolysates that were proved to enhance iron uptake by Caco-2 cells. The objectives of this study were to investigate effects of components of hydrolysates and digestion products of hydrolysates of neutrase treated WPC on iron uptake. The hydrolysates of WPC treated with neutrase were separated by ultrafiltration. Effect of different components of hydrolysates on iron uptake was studied by in vitro digestion combined with Caco-2 cell model. The results showed that low-molecular components (below 10kDa) enhanced iron bioavailability significantly (p<0.05). The components of 3 kR（3~10kDa）and 3kF（below 3kDa）increased iron bioavailability to 23.32% and 24.23%, respectively, compared to untreated WPC (2.58%). Bioavailability of iron from ferrous sulfate added with different components of the hydrolysates was significantly associated with iron absorption (r=0.935, p<0.01), while there was no significant relation between iron dialyzability and bioavailability. The hydrolysates of neutrase treated WPC was digested by pepsin and trypsin gradually to obtain the digestion products, and then separated into four components of differentmolecular weight by Sephadex G-25. Iron absorption was studied by Caco-2 cells. The results suggested that the components at molecular weight no more than 1kDa significantly (p<0.05) increased iron absorption to 90.47% compared with 25.13% in the control, while the components with molecular weight at 1~5kDa acted as inhibitor.